1. Field of the Disclosure
The present disclosure relates to a molded case circuit breaker, and particularly, to a molded case circuit breaker capable of preventing a dielectric breakdown due to leakage of arc gas occurring during a short-circuit.
2. Background of the Disclosure
Generally, a molded case circuit breaker (MCCB) is an apparatus provided with a switching mechanism, a trip unit, etc. integrally assembled to each other in a case formed of an insulating material. An electrical path, which is being used, may be open or closed manually or by an electric adjuster provided outside the case. When an overload, a short-circuit, etc. occur, the molded case circuit breaker serves to automatically disconnect the electric path.
If a short-circuit has occurred on a molded case circuit breaker for 3 phases, a trip unit installed in the molded case circuit breaker disconnects an electric path by separating contacts from each other. In this case, arc is generated when the contacts are separated from each other, and the arc gas in a plasma state is discharged to outside through an arc gas vent means provided in the molded case circuit breaker.
FIG. 1 is a perspective view for explaining a vent means for a molded case circuit breaker according to the cited reference D1 of the prior art.
Referring to FIG. 1, arc gas generated from inside of an interrupter assembly 70 is discharged to a chamber region 100 through an outlet 80 provided at a lower end of the interrupter assembly 70. The arc gas is diverged to two sides in the chamber region 100, through a gas divergence portion 100 of a triangular shape. Then the arc gas is discharged to outside through a chute 90.
However, the arc gas discharge structure of D1 (U.S. Pat. No. 7,034,241) has the following problems. When an auxiliary case (not provided in D1) is coupled to a case 190, an arc leaks to a gap between the case 190 and the auxiliary case, on a passage between the outlet 80 of the interrupter assembly 70 and a terminal portion. As a result, an arc conducting path is formed on the surface of the case 190 and the auxiliary case, and thus a dielectric breakdown occurs between conductors and a bottom surface of the case 190. This may cause a dielectric strength against a reference withstand voltage of 2.2 KV, to be lost.